allparts sell the tremol-no which replaces the spring claw, so no drilling necessary. it has two thumb screws, giving you the options of full floating, dive only (which is what that screw thing you've pictures would do) or hardtail. i have one in a Patrick Eggle Los Angeles, and it works perfectly.
no doubt more expensive than that trem-stop, but more versatile and easier to use. with the thumb screws you can change settings instantly.